_.findLastIndex

_.findIndex scans left to right. _.findLastIndex does the same search from the right, so it returns the index of the match closest to the end of the array. Everything else is identical: run a truth test per element, return the first index that passes, hand back -1 when nothing does.

It's one of the auto-generated _.* wrappers in sfinktah/comfy-ovum, built on underscore3 (a Python port of Underscore.js). The whole family shares one design, and this one is the "array method" variant, so the primary input is named py_list.

When you'd use it

Any time "the last one that matches" is more meaningful than "the first." Think of a list of generations or intermediate results where you want the most recent item that satisfies a condition - the last tag with a confidence above a threshold, the last frame that had a face detected. Because the output is a plain INT index, it drops straight into indexing, slicing, or loop-cursor nodes. -1 is the "not found" signal you branch on.

The inputs that matter

• py_list - the array to search (loose *; also accepts a _.CHAIN).
• predicate - the truth test, ANY input.
• predicate_json - the practical one. When predicate isn't connected, this multiline string is parsed as JSON or used as a selector. A key name in quotes - "ok" - finds the last item where that key is truthy; an object like {"ok": true} does shorthand matching; a number compares values directly.

Output is typed INT, which is rare and useful in this family - most of its siblings return a loose *.

Install

Same as the rest of the pack. ComfyUI Manager, search "comfy-ovum", or:

cd ComfyUI/custom_nodes
git clone https://github.com/sfinktah/comfy-ovum

Restart, look under ovum/underscore. No models, no downloads.

Honest warnings

The author's README disclaimer covers this whole family: work in progress, not for production. Also note the subtle behavioral point - reverse iteration means if your predicate matches every element, you get the last index (len-1), not 0; people expecting "first match" semantics get surprised here. And remember predicate_json needs strict JSON: quote your key names.